Micronutrient deficiency in plane tree leaves during summer in arid and semi urban landscapes causes chlorosis and reduced vitality. Trunk injection of targeted fertilizers offers an effective, eco-friendly solution to address deficiencies while minimizing environmental pollution. This study evaluated the effects of trunk injections of iron sulfate (0%, 1%), zinc sulfate (0%, 0.5%, 1%), and manganese sulfate (0%, 0.25%, 0.5%) in eleven fertilizer formulations on morphological and biochemical traits, including antioxidant enzyme activities, in plane trees. The combination of Fe 1% + Zn 1% + Mn 0.25% was most effective, increasing leaf fresh weight by 35.2%, dry weight by 37.4%, and leaf area by 38.4% compared to controls. Total soluble carbohydrates rose by 74.9% with Fe 1% + Mn 0.25%, which also yielded the highest leaf protein content. Fertilizer treatments reduced leaf hydrogen peroxide and malondialdehyde levels, indicating enhanced stress tolerance, with the greatest reductions seen in Fe and Mn combinations. Peroxidase activity generally decreased under fertilization—most with Fe 1% + Zn 1%—while superoxide dismutase activity showed variable effects. Leaf micronutrient contents, especially Fe, Zn, and Mn, significantly increased with treatments, peaking with the optimal fertilizer mix. These results highlight the importance of specific micronutrient combinations in improving tree health by modulating biochemical processes and stress resilience. This suggests that tailored fertilization via trunk injection can enhance urban tree vitality and quality. Future studies should explore long-term effects and alternative micronutrient sources to optimize urban forestry management in diverse environments.
